Welcome, as you have already seen there are a lot of wonderful folks here and you can learn from many of our mistakes and advice.
Your wife has done something that will take both of you years to get through, so don't worry about having a decision today, tomorrow, next week or next month.
I think it is hopeful that she is already seeing a therapist, but I also think that you need to attend a session with her, and make sure that she has put it all out there, the drinking, the affair, all of it. The therapist can't help her if she is giving her a song and dance, and not dealing with the real issues at hand.
You should definitely look into alanon, going to AA is for her. Alanon is for you. Being a partner of an alcoholic is just as difficult as being an alcoholic. You deserve to understand the process of addiction, the changes it causes, and the impact it has on you.
If you don't feel you can 180 now, don't. What you do need to do is give her your list of dealbreakers with consequences.
She absolutely has to get off the computer, that gaming and EA is as much as an addiction as the alcohol.
She has to go NC with this douche, and send him a note stating so.
She has to be transparent.
She has to stop drinking.
You will find you are more in the role of a support person than actually getting to deal with your pain as she initially withdraws from her addictions. It's not right, it's not fair, but it is what happens. That is why you have to reach out for support. Her parents, if supportive and not the underlying cause of her addictions can help. Your parents can support you as well.
Make sure that you are taking time for you. That you are eating, if you aren't eating at least getting some protein shakes down. That you are sleeping (at least 5 hours every couple of days). Sleep is essential to keeping the emotions in check, and making calm rational decisions, if you are struggling with it, contact your Dr. Let them know what is going on (they see it everyday and will not judge) and see if meds can help even temporarily.
YOU deserve to be loved, and respected and cared for too. Make sure that you do this for yourself right now.